On Thu, Aug 28, 2025 at 12:01:16AM +0200, David Hildenbrand wrote:
> Now that a single folio/compound page can no longer span memory sections
> in problematic kernel configurations, we can stop using nth_page().
>
> While at it, turn both macros into static inline functions and add
> kernel doc for folio_page_idx().
>
> Reviewed-by: Zi Yan <z...@nvidia.com>
> Signed-off-by: David Hildenbrand <da...@redhat.com>
LGTM, so:
Reviewed-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.com>
> ---
> include/linux/mm.h | 16 ++++++++++++++--
> include/linux/page-flags.h | 5 ++++-
> 2 files changed, 18 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 2dee79fa2efcf..f6880e3225c5c 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -210,10 +210,8 @@ extern unsigned long sysctl_admin_reserve_kbytes;
>
> #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
> #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
> -#define folio_page_idx(folio, p) (page_to_pfn(p) - folio_pfn(folio))
> #else
> #define nth_page(page,n) ((page) + (n))
> -#define folio_page_idx(folio, p) ((p) - &(folio)->page)
> #endif
>
> /* to align the pointer to the (next) page boundary */
> @@ -225,6 +223,20 @@ extern unsigned long sysctl_admin_reserve_kbytes;
> /* test whether an address (unsigned long or pointer) is aligned to
> PAGE_SIZE */
> #define PAGE_ALIGNED(addr) IS_ALIGNED((unsigned long)(addr), PAGE_SIZE)
>
> +/**
> + * folio_page_idx - Return the number of a page in a folio.
> + * @folio: The folio.
> + * @page: The folio page.
> + *
> + * This function expects that the page is actually part of the folio.
> + * The returned number is relative to the start of the folio.
> + */
> +static inline unsigned long folio_page_idx(const struct folio *folio,
> + const struct page *page)
> +{
> + return page - &folio->page;
Ahh now I see why we did all this stuff with regard to the sparse things before
:) very nice.
> +}
> +
> static inline struct folio *lru_to_folio(struct list_head *head)
> {
> return list_entry((head)->prev, struct folio, lru);
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 5ee6ffbdbf831..faf17ca211b4f 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -316,7 +316,10 @@ static __always_inline unsigned long
> _compound_head(const struct page *page)
> * check that the page number lies within @folio; the caller is presumed
> * to have a reference to the page.
> */
> -#define folio_page(folio, n) nth_page(&(folio)->page, n)
> +static inline struct page *folio_page(struct folio *folio, unsigned long n)
> +{
> + return &folio->page + n;
> +}3
>
> static __always_inline int PageTail(const struct page *page)
> {
> --
> 2.50.1
>
